Glycosylation: The covalent addition of the sugar moities to N or O atoms present in the side chains of various amino acids of certain proteins, usually occuring within the Golgi apparatus during the secretion of a protein. The glycosylation sites are basically partially predictable by the current computer searches for the relevant motifs in protein sequence. Glycosylation might have profound but quite unpredictable effects on the stability, folding, and antigenicity of the secreted proteins. The glycosylation is a property of the eukaryotic cells, and differs among the different cell types (that is it might be quite different in yeast or insect cells used for the protein expression, when compared with the Chinese hamster ovary (CHO) cells).